Interpretive Summary: To assess an animal's welfare requires an amalgam of measures, such as behavior, physiology, immunology, productivity, pathology and neuroendocirnology. Whereas some of these measures are easy to take without interacting with the animal, other measures often require the animal to be restrained for a sample to be taken, such as a blood sample. This runs the risk of having the restraint and human-animal interaction during the sampling causing a stress response which may mask the effect of the actual stressors that you are trying to measure. We developed a housing system that enabled us to maintain catheterized pigs from which we could take blood samples automatically, without any human restraint or interaction. We then compared stress hormones in these blood samples, with those taken from restrained and manually-sampled pigs and also with samples taken using the automatic system when other pigs were being manually sampled in the same room. We found that there was no difference in our stress hormone concentrations (cortisol and noradrenalin) between both sets of our automatically-sampled blood samples. This means that the sights and sounds of other pigs being restrained and blood sampled did not appear to induce any "empathetic" stress response in the automatically-sampled pigs. However, the major result was that the stress hormone concentrations in the blood of the restrained and manually-sampled pigs were between 2 and 3 times higher than those of the automatically-sampled pigs, demonstrating that the sampling method can indeed have a large impact. The system we developed has the potential to be used to measure a pig's discreet reponses to imposed stressors of interest, for example heat stress, safe in the knowledge that we are measuring that stressor alone and not influencing the results by our own actions.

Technical Abstract:
Minimizing the effects of restraint and human interaction on the endocrine physiology of animals is essential for collection of accurate physiological measurements. Our objective was to compare stress-induced cortisol (CORT) and noradrenalin (NorA) responses in automated versus manual blood sampling in pigs. A total of 16 pigs (30 kg) were assigned to either (i) automated blood sampling via an indwelling catheter using a novel penning system called PigTurn®, which detects the pig’s rotational movement and responds by counter-rotating, allowing free movement while preventing catheter twisting; (ii) automated sampling while exposed to visual and auditory responses of manually sampled pigs; (iii) manual sampling by jugular venipuncture while pigs were restrained in dorsal recumbency. During sampling of (i), personnel were not permitted in the room; samplings of (ii) and (iii) were performed simultaneously in the same room. Blood samples were collected every 20 min for 120 min and measured for CORT (ng/ml) using mass spectrometry and NorA (pg/ml) using HPLC. Effects of treatment and time were computed with mixed models adjusted by Tukey post-hoc. CORT and NorA concentrations were lowest in group (i) followed by group (ii), which were not different (CORT = 27.0 ± 2.1 and 32.7 ± 2.7 ng/ml, NorA = 260.9 ± 47.4 and 268.5 ± 54.8 pg/ml; P > 0.1). However, CORT and NorA levels in manually sampled animals (iii) were highest (CORT = 41.0 ± 2.3 ng/ml, F2,13 = 4.74, P < 0.05; NorA = 747.0 ± 61.5 pg/ml, F2,11 = 24.81, P < 0.001) compared to automated methods (i) and (ii). Plasma concentrations across time were not different for CORT (F6,71 = 0.61, P > 0.1), but NorA concentration at time 0 min (610.8 ± 59.0) was higher than at 120 min (380.7 ± 52.0; F6,63=3.54, P < 0.01). The presence of visual and auditory stimuli evoked by manual sampled animals did not affect non-handled pigs’ responses. Restraint and manual sampling of pigs can be extremely stressful while, the automated blood sampling of freely moving pigs, housed in the PigTurn®, was significantly less stressful for the animals.